The files of government departments are supposed to go to the National Archives.  That would be your first place to look.

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From: Association for Recorded Sound Discussion List <[log in to unmask]> on behalf of Filip Šír <[log in to unmask]>
Sent: Wednesday, September 4, 2019 10:28:40 AM
To: [log in to unmask] <[log in to unmask]>
Subject: [ARSCLIST] Informations about OWI archive

Dear colleagues,

we are now in process of research George Voskovec and Jan Werich recordings
for OWI during WWII.

We would like to know if there is any kind of information about archive of
OWI connect with broadcast to Czechoslovakia. We appreciate your help and

Many thanks

Best regards

Filip Sir
Czech Republic